INTRODUCTION

• Pathology literally means the study (logos) of suffering (pathos)
• Pathology is the study of the structural, biochemical & functional changes in cells, tissues & organs that underlie disease
• By the use of molecular, microbiologic, immunologic & morphologic techniques, pathology attempts to explain the whys and wherefores of the signs and symptoms manifested by patients while providing a rational basis for clinical care & therapy
• It is thus a bridging discipline involving both basic sciences & clinical practice
• It is also the scientific foundation for all medicine

DIVISIONS OF PATHOLOGY

• Traditionally, the study of pathology is divided into;
  • General pathology &
  • Systemic pathology

General Pathology

• General pathology is concerned with the common reactions of cells & tissues to injurious stimuli
• Such reactions are often not tissue specific
• Acute inflammation in response to bacterial infections produces a very similar reaction in most tissues

Systemic Pathology

• Systemic pathology, on the other hand, examines the alterations and underlying mechanisms in organ specific diseases such as ischaemic heart disease

ASPECTS OF DISEASE PROCESS

• There are 4 aspects of a disease process that from the core of pathology:
  • Its cause (etiology)
  • The biochemical & molecular mechanisms of its development (pathogenesis)
  • The structural alterations induced in the cells & organs of the body

(morphological changes), &

• The functional consequences of these changes (clinical manifestations)

Etiology

• The initiating cause of a disease
• Can be genetic or acquired

Genetic and environmental factors may combine to produce a diseases state e.g. hypertension, diabetes mellitus (DM), asthma, cancers and schizophrenia

Please NOTE;

• One causative agent may be responsible for specific diseases e.g. leprosy and M. leprae  Several aetiological agents may produce specific disease e.g. ü Meningitis – E. coli, H. influenzae, Pneumococcus
  • Lobar pneumonia – pneumococcus, staphylococcus
  • Lung abscess – Staphylococcus bacteriodes
• Some causative agents may produce structural/morphological changes that are specific  Several diseases have unknown aetiology e.g.
  • Crohn’s disease
  • Ulcerative colitis ü Sarcoidosis, etc.

Pathogenesis

• Refers to the sequence of cellular, biochemical and molecular events that follow the exposure of cells or tissues to an injurious agent
• Explains how the underlying aetiologies produce the morphologic & clinical manifestations of the disease
• Remains one of the main domains of Pathology
• Even when the initial cause is known, it is many steps removed from the expression of the disease

Morphological Changes

• Refers to the structural alterations in cells or tissues
• Can be unique and specific and therefore characteristic of the disease or diagnostic of the aetiological agent
• Some are visible to the naked eyes and are called GROSS CHANGES
• Others are visible only with the aid of light microscope and are called

HISTOPATHOLOGICAL CHANGES

• Others require electron/scanning electron microscopes and are referred to as

ULTRASTRUCTURAL CHANGES

Functional Derangements & Clinical Manifestations

• The end results of genetic, biochemical and structural changes in cells and tissues are functional abnormalities
• These lead to the clinical manifestations (symptoms and signs) of disease, as well as its progress (clinical course and outcome)
• Hence, clinicopathologic correlations are very important in the study of disease

Summary: Cell Pathology